Sighting device



March 21, 1944. c. G. AXTMANN SIGHTING DEVICE Filed July 28, 1941 s Sheets-Sheet 2' INVENTOR BY M NNN Cups/ms 6. Axr/mA/A/ aw Y Mun QNN Q \ww 2.35 .3 .35 Ex Q9.

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March 21, 1944'.

2. 5. AXTM'ANN SIGHTING DEVICE Filed July 28, 194

3 Sheets-Sheet 3 Ayn/ANN INVENTOR V Patented Man-21, 1944 UNITED STATES PATENT. OFFICE SIGHTING DEVICE I Clarence G. Axtmann, Sacramento, Calif.

Application July 28, 1941, Serial No. 404,329

' 13 Claims.

My invention relates to aflring device and has particular reference to a combined sighting and bomb release device for use on aircraft.

Many attempts have been made prior to myinvention to provide a bomb sight which would operate with sufficient accuracy in high altitude bombing practice to make such practice'effcctive and insure a high percentage of true hits on the target or bombed objective. These attempts have not been entirely successful for the reason that the present devices are greatly dependent upon the manner in which the devices are used and also upon close and accurate coordination between the bombardier and the pilot of the aircraft.

For example, one of the earlier types of bomb Sights included a mechanism for establishing a sighting line as by means of a telescope having cross-hairs in the eyepiece, the inclination of the sighting line being established prior to the release of the bomb and being determined by the altitude and speed of the aircraft. With this mechanism the bombardier was required to Watch through the sighting device and manually release the bomb at the time the image of the objective appeared centered on the cross-hairs. The difficulty in releasing the bomb at precisely the right point will be readily appreciated when it is realized that the velocity of the aircraft is usually around aircraft in its proper course with respect to the target. Due to the difficulty in coordinating the guiding of the aircraft with the bombardiers instructions it was seldom possible to so direct the plane as to position the plane in the proper location and on the proper course at the instant of bomb release.

The prior bomb sights also required that the aircraft be maneuvered according to a prearranged plan; that is, once the sight was set for a given altitude, speed and course, it was necessary for the pilotto so fly the plane. While any deviations from the pre-arranged plan seriously affected the accuracy of the bombing, the pilot had no way of knowing how accurately he was following such plan except by reference to the conventional flight instruments and to instructions from the bombardier. This required close attention on the part of the pilot and often at a time when he was being continually harassed by anti-aircraft fire and enemy fighting planes.

It is, therefore, an object of my invention to provide a bomb sight including means for determining the bomb release point from the conditions existing immediately prior to the release of the bomb.

It is also an object of my invention to provide a bomb sight which includes means for continually adjusting or correcting the determination of the bomb release point in accordance with changes in the conditions affecting the location of such point.

It is a still further object of my invention to provide a bomb sight of the character set forth in the preceding paragraphs which includes.

means for correcting the determination of the bomb release point as it may be affected by air currents or winds.

It is also an object of my invention to provide a bomb sight of the character set forth in the preceding paragraphs which includes a universally mounted sighting device adapted to be maintained trained on the target or objective and a coacting means for automatically releasing the bomb when the aircraft arrives at the correct bomb release point.

It is an additional object of my invention to provide a bomb sight of the character set forth in the preceding paragraphs which includes a means coacting with the sighting device for continually informing the pilot of the aircraft as to the relation between the then course of the plane and the correct course.

It is a still further object of my invention to provide a bomb sight of the character hereinbefore referred to which includes a means for reproducing in the aircraft and at a reduced scal the trajectory of the bomb under the conditions existing at the instant of bomb release of all correct bo'db release points and for a given wind component parallel to the course of the plane and which includes a sighting device adapted to be maintained trained on the objective and coupled to an indicator representing on the curve the sight line of the sighting device, the indicator being operable to automatically release the bomb when the intersection of the sight line with the curve progresses therealong to a point corresponding to the altitude of the aircraft.

Other objects and advantages of my invention will be apparent from a study of the following specifications, read in connection with the accompanying drawings, wherein:

Fig. 1 is a fragmentary perspective view of the interior of an aircraft illustrating the general appearance and manner of installation of the preferred embodiment of my invention;

Fig. 2 is a chart or graph indicating by means of curved lines the trajectories of bombs for a number of bomb release points and the locus of all correct bomb release points for a given speed of the aircraft;

Fig, 3 is a perspective diagram illustrating diagrammatically the relation between the objective and the bomb release point and the manner in which correction is made in the location of the bomb release point to compensate for air cur-- taken substantially along the line v1-v1 of Fig.

4; and

Fig. '7 is a diagrammatic illustration of one form of mechanism which may be employed for interconnecting the sighting device with an indicating device mounted on the instrument panel of the plane in a position to be observed by the pilot of the plane. Referring to the drawings, I have illustrated in Fig. 2 by means of a, chart or graph the trajectory I of a bomb released at the point A at an altitude of approximately fourteen thousand feet and ahorizontal distance of approximately eighty-eight hundred feet from the bombed objective O. The curve I is parabolic in form if the effect of the air resistance on the line of the bomb is neglected. The first part of the following discussion is based on the assumption that the effect of such air resistance is neglected.

The trajectory I is in the form of a parabola for the reason that the forward velocity of the bomb at the instant of bomb release is equal to the forward velocity of the plane at that instant and this forward velocity continues .undiminished until the bomb strikes the ground. The vertical velocity on the other hand accelerates from zero at the instant of bomb release to a maximum value at the time the bomb strikes the ground, this acceleration resulting from the effect of the gravity on the bomb. The curve I represents the trajectory under the aforementioned conditions when the ground speed of theplane is two hundred miles per hour.

If instead of flying at an altitude of fourteen thousand feet the plane were flying at an altitude of ten thousand feet, then the bomb would have to be released at the point B in order for it to fall on the objective 0, the trajectory in this lattter case being represented by the curved line 2.

A comparison of the-curves I and 2 indicates that they are sections of the same parabola and a that the origins A and B lie on an inverted parabolic curve 3 which is of the same form and shape as the curves I and 2 but with its origin located at the objective 0. The curve 3 thus represents the locus of the bomb release points A and B and likewise represents the locus of all correct bomb release points for a ground speed of two hundred miles per hour.

Similarly the curve 4 represents the locus of all correct bomb release points for a plane velocity of three hundred miles per hour and it will be noted that the curve 4 is of the same form as a bomb trajectory 5 resulting from releasing a bomb at a point C. It is thus apparent that in order to determine the correct bomb release point, it is necessary only to construct a locus curve such as the curves 3 and 4 for the particular forward velocity of the plane at the instant of bomb release, whereupon the horizontal positioning of the bomb release point with respect to the objective 0 may be determined by observing the intersection of this locus curve with the horizontal line on the chart representing the altitude of the plane.

Thus from Fig. 2 it may be determined that for an altitude of ten thousand feet and a ground speed of three hundred miles per hour the horizontal distance from the objective to the bomb release point is substantially eleven thousand feet (release point C). Similarly at a forward speed of two hundred miles per hour the bomb release point for an al tude of ten thousand feet (point readily calculated from test data with respect to each type of bomb and giving the flight characteristics of the bomb.

Air resistance has, however, a further and more important effect on the flight of the bomb which resides in the deflecting of the bomb from the ideal trajectory whenever there is a wind blowing. The reference made hereinbefore with respect to the speed of the plane represents the speed of the plane relative to the surface of the ground. A head or tail wind tends to slow down or increase, respectively, the forward speed of the bomb after the bomb is released and similarly a cross wind tends to deflect the bomb laterally of the vertical plane in which the course of the plane lies at the instant of bomb release.

These considerations are represented diagrammatically in Fig. 3 wherein the plane DO'E represents the sea level plane and the plane FOG represents the plane of elevation of the objective 0. If there is no wind whatever the correct course of the aeroplane is along a line HJ and the current release point is located at K, the bomb upon release following the trajectory indicated by the dotted line 6. The bomb release point K may be determined by reference to locus curves as previously described in connection with Fig. 2.

If, however, instead of there being no wind ,HJ above the objective plane FOG.

whatever there is a wind component in the direction oi flight of the plane: 1. e., in a direction correct bomb release point is situated at L spaced from the release point K by a correction distance indicated by the dimension line 1 in Fig. 3. A bomb released at the point L under these circumstances will follow a substantially parabolic trajectory indicated by dotted line 8 in Fig. 3.

The distance Lot course, depends upon the length of time the head or tail wind component acts on the bomb and this is, of course, a non-linear function of the altitude of the plane's course However, the magnitude of the correction distance I is ordinarilv relatively small with respect to the horizontal distance GO and consequently for all practical purposes the head or tail wind correction distance 1 can be considered as being a linear function of both the magnitude of the head wind component and the altitude GL of the plane at the instant of bomb release.

If, in addition to there being a head wind component, there is also a wind component directed.

normal to the course of the plane; i. e., in the direction indicated by arrow 9 in Fig. 3, then it is necessary to alter the course of the plane from the course represented by the line HJ to a laterally off-set course represented by the line MN. The amount of this lateral off-set which is indicated in Fig. 3 by arrow IO permits the bomb to drift in the direction of the arrow 9 during its fall parallel to the line HJ, it will he found that the so that a bomb released at a release point P will follow the substantially parabolic trajectory indicated by the solid line i l in Fig. 3.

The corrective distance In like the corrective distance i is dependent upon the amount of time the cross wind component acts on the bomb and this is in turn a non-linear function of the altitude of the plane at the instant of bomb release. However, the corrective distance I0 is ordinarily small with respect to the horizontal distance 0G with the result that for all practical purposes the corrective distance [0 can be considered as being a straight linear function of both the altitude GL of the plane and the magnitude of the cross wind is included in a sloping plane NOGP and the amount of cross wind correction may be conveniently represented by the angle of inclination of the plane NOGP from the vertical, this angle being indicated in Fig. 3 by the arcuate dimension line l2.

From the foregoing it is apparent that the uncorr'ected bomb release point K may be readily ascertained by employing a locus curve such as that described with reference to Fig. 2 for the speed of the plane with respect to the ground sur- ,face, this bomb release point being identified by the horizontal distance of the release point from the objective for the particular altitude at which the plane is flying.

By making appropriate linear corrections for I both head wind and cross wind components the I have illustrated in Fig. l a sighting and bomb release mechanism embodying the principles above discussed. The preferred form of this device is arranged to be operated by two operators. a bomberdier and an observer. The observer may be provided with a seat H adjacent a universally mounted sighting instrument it which may conveniently comprise a telescope of suitable magnitying p wer and having cross-hairs provided in the eye-piece thereof. The bombardier may be provided with a seat It positioned adjacent the sighting and fire control devices indicated generally by the reference character II.

This device is interconnected with the telescope Ii and is also connected by means or a suitable transmission system 18 to a. panel indicator I. mounted upon the instrument panel 28 in the pilot's cockpit for the purpose of continually ap- Drising the pilot of the plane as to the relation between the then course of the plane and the bomb is to strike its objective.

The construction of the mechanism I1 is best illustrated in Figs. 1 and 4 as comprising a base structure 2! which is mounted for pivotal movement about a vertical axis as by means or a suitable supporting post 22. The base frame 2! may carry a pointer 23 which is movable over a calibrated quadrant 24 to permit the positioning of the instrument I! at a predetermined angle with respect to the axis or the plane. position 0! the base frame 2| will be so adjusted as to dispose the fore and aft axis of the device parallel to the track of the aircraft or its true course relative to ground surface. In order to so position the base frame 2!; it is necessary to set the pointer 23 on the quadrant 26 at an angle corresponding to the drift angle of the plane, it being recognized that in case there is a cross wind component the longitudinal axis of the plane will not b parallel to the actual course of the plane with respect to the ground surface.

Upon the base frame 2| I position a curve gencrating apparatus indicated generally by the reierence character 25 and a control or indicating apparatus indicated generally by reference character 26 which is employed to actuate the curve generating apparatus 25.

The curve generating apparatus 25 preferably comprises a plurality of parallelly extending members 2'! which may, as is illustrated in Fig. 5, be of a substantially T-shape disposed in abutting relation to each other to define a plurality of guiding channels 28. Within each of the channels 28 I position a slidable block member 29 within which is mounted a rotatable support 30 adapted to be moved in pivotal fashion about a vertically disposed axis. From the support 30 a pair of spaced pins 3| extend upwardly. Each of the pin members is surrounded by a roller 32 and the adjacent surfaces of the rollers 32 are so spaced as to closely embrace the sides of a rectangular tape 33 formed of spring steel or other suitable flexible and highly resistant material. The tape 33 is disposed edgewise; that is,

with its width disposed in a vertical plane and the width of the tape 33 is sufficient to dispose the upper edge 3 thereof well above the upper ends of the pins 3! and rollers 32.

The tape 33 has one end fixed as indicated at 35 in Fig. 4 and Fig. 5 to a stub shaft 38 supported on the base frame 2|. The center or this stub shaft constitutes the origin or pivotal point about which the tape 33 is moved and about which other mechanism to be described hereinafter is moved. This point will hereinafter be referred to as the origin."

Ordinarily the carried by suitable uprights 44.

The bands 31 are formed of spring steel or other suitable material and are stretched very tight so that rotation of the shaft 4| and the step cone pulley 39 produces a precise and predetermined sliding movement of the block memhers 29 along the channels 28. The diameters of each of the band engaging steps 38 of the pulley 39 are so determined with respect to each other that rotation of the shaft 4| positions the block members 29 in positions lying along a. parabolic curve having its origin at the origin of the device.

The pulley 38 is so arranged that irrespective of the angular position of the pulley 39 the block members 29 will all lie on a parabolic curve. Since the pin and roller members 32 of each of the block members 29 engage opposite sides of the tape 34, it will be seen that the tape is thereby forced into a true parabolic curve. This curve constitutes a locus curve such as the curves 3 and 4 described with reference to Fig. 2 and the adjustment of the abscissa of this curve by rotating the pulley member 39 serves to adjust the shape of the locus curve to correspond to different speeds of the aircraft with respect to the ground surface.

In order that a locus curve of the proper equation may be readily and accurately formed by the bombardier. the shaft M is extended into the control apparatus 26 and journaled at its far end as by means of a suitable bearing 45. The shaft 4| is secured to a spider 46 upon the opposite arms of which are journaled bevel gears 41 and 48, These bevel gears mesh with double-faced bevel gears 49 and 50 which are independently rotatable upon the shaft 4|. One of the bevel gears 59 is engaged by another bevel gear 5i which may be driven by a suitable hand crank 52.

Assuming for the time being that the bevel gear 49 is held against rotation, it will be seen that rotation of the crank 52 will be translated through the gears Stand 53 and through the spider gears 41 and 48 into a. rotation of the spider 4E and consequently into a rotation of the shaft .4l. Thus, the crank 52 may be employed to adjust the equation of the locus curve generated by the tape 34.

The crank 52 is also connected as by means of a gear train to the pointer 53 of an indicating prises the locus of all correct bomb release points for that particular speed of the plane.

As was pointed out pieviously, to find the actual release point on the locus curve it is necessary to ascertain the intersection of this locus curve with the horizontal line representing the altitude of the plane. Accordingly I provide along the fore and aft edges of the base frame 2! a pair of identical feed screws 56 and 58 Journaled at opposite ends as by means of suitable bearings 51. Between the feed screws 55 and 56 and threadedly engaged with each I provide an elevator bar 58. By synchronously rotating the feed screws and 55 the bar 58 may be caused to move in the direction of the axis of the parabola defined by the curve generator band 34 and consequently may be employed to represent the altitude of the plane with respect to the objective which is represented by the origin of the curve 34.

In employing the sighting device, the elevator bar 58 must, therefore, be set by the bombardier in a position corresponding to the altitude of the plane with respect to the objective. Accordingly the feed screws 56 and 56 are extended into the control mechanism 26 and are provided on their outermost ends with bevel gears 59 and Gil mes ng, respectively, with bevel gears 6i and 62 secured to a cross shaft 83 journaled upon the base frame 2| as by means of suitable journals 64.

The shaft 63 may be driven from a shaft 65 as by means of a bevel geared interconnection 66, 57.

The shaft 851s secured to a spider 88 of a differential or mixing gear arrangement identical with the difierential 45-50 previously referred to. One of the driving gears of this differential is drivably engaged with a crank 65 and'the other is drivably engaged with a crank in so that rotation of either of these cranks will result in a rotation of the cross shaft 63 and consequently in a corresponding synchronous rotation of the feed screws 55 and 86.

The crank I0 is also connected as by means of suitable gearing to a pointer H adapted to indicate on a dial 72 the altitude of the plane above sea level, and the crank 69 is similarly connected to a pointer 13 adapted to indicate on a dial (4 an altitude which may be the known or previously determined altitude of the target or objective above sea level.

The gearing employed to interconnect the cranks 69 and ill with the cross shaft 63 and with the pointers H and T3 is so arranged that when the pointer H is moved to a point indicating the altitude of the plane above sea level and the pointer 13 is moved to a point indicating the elevation of the target or objective above sea level the net rotation which is imparted to the cross shaft 63 comprises the difference between this altitude and this elevation. Thus, the elevator bar 58 is moved along the axis of the locus curve 34 a distance corresponding to the elevation of the plane above the objective. The point of intersection of the elevator bar with the locus curve 34 provides an indication of the horizontal distance between the correct bomb release point and the objective, this distance being measured in the direction of the length of the elevator bar and comprising the distance from the point of intersection to the longitudinal axis of the parabola passing through the origin.

This point of intersection may be readibr indicated by forming the elevator bar 58 with an elongated slot-like opening 15 in which is slldably supported an intersects: car '55. The opening 55 serves to guide the car l6 for sliding movement parallel to the length of the elevator bar 58 and transverse to the axis of the parabola and the car may be mounted for such slidable movement as by providing a pair of transversely extending pins or of that portion of the band 34 which passes under the elevator-bar 58, the flanges of the pulley 80 being disposed on opposite sides of the band 34.

Thus, as the shape of the curve 34 is changed by rotating the step cone pulley 39 and as the position oi the elevator bar 58 is changed by rotating the feed screws 56 and 68, the car 18 slides along the elevator bar 58 in such manner as to maintain the center of the spindle 19 at precisely the intersection of the band 34 with the axis of the elevator bar 58.

The spindle 19 thus represents on the curve generator mechanism the location of the correct bomb release point with respect to the objective which is represented by the origin of the device. Similarly, therefore, a straight angularly disposed line extended between the origin and the spindle 19 represents a line of sight between the bomb release point and the objective. This representative sight line is indicated on the curve generator by a sight line indicator 8i comprising a long thin arm member which is secured to a sector gear 82 mounted for tree rotation upon the stub shaft 36. The sector gear 82 is drivablvengaged with the telescope is in such manner that the angular position of the sight line indicator 8i with respect to the axis 01' the locus curve 34 corresponds to the angular position 0! the actual sight line between the plane and the objective assuming the telescope i5 is trained on the objective.

The telescope I5 is therefore provided with a supporting collar 83 which may be clamped as by means of a screw 84 to the tube of the telescope i5 and which provides a pair of trunnions 65 dlsposed at right angles to the axis of the telescope. These trunnions are received in suitable bearing openings formed in a fork member 85 which is in turn secured to or formed integrally with a hollow shaft 8'! journaled for rotation in a suitable bearing 88 mounted-upon a bracket 89 secured to the base frame 2i. The inner end of the shaft 87 carries arbevel gear 90 which is meshed with the sector gear 82, the diameters of the gears 82 and 90 being so adjusted that the sight line indicator 8| is moved the same angular distance as the telescope is moved about the horizontal axis of the shaft 87.

Assuming that there is neither cross wind nor head wind, the device is operated as follows. The bombardier sets the pointer 23 on the quadrant 26 to a position aligning the axis of the sighting device I! with the axis of the plane. He then sets on the dial and pointer fail-5t, by

' means of the crank 52, the forward speed of the plane with respect to the ground. The cranks E9 and 79 are employed to set the dials 'l3-'M and ll-12 to the altitude of the plane and to the elevation of the objective. This operation serves to generate by means of the curve generator band a locus curve for all correct bomb release points at the particular plane speed and serves to position the spindle 19 at a point corresponding to the correct bomb release point for the particular elevation of the plane with respect to the objective. Should the speed of the plane very or should the elevation of the plane vary the bombardier may, by means of the cranks B2 and 10, make the appropriate correc tion to the shape 01' the curve and the location or the spindle l9.

as soon as the objective is sighted, the observer trains the telescope i5 thereon and so positions the sight line indicator 8i in a position corresponding to the actual line oi sight between the plane and the objective, such as that illustrated in Fig. 4. Thereafter the observer merely moves the telescope i5 slowly in such manner .as to maintain the image 01 the objective centered on the cross-hairs in the eyepiece, this slow movement of the telescope being. or course, re-

quired by the approach of the aircraft toward the objective.

As the telescope is thus slowly moved the sight line indicator 8i is likewise slowly moved pivotally in a counter-clockwise direction as viewed in Fig. 4. The correct instant of bomb release is determined by observing the instant at which the sight line indicator 8i coincides with a straight line drawn between the origin and the spindle 19. When this condition obtains, the bomb mayv be released manually if desired. However. I prefer to automatically release the bomb at this instant in order to avoid the other wise unavoidable human errors which result from a manual release.

Accordingly the sight line indicator BI is positioned closely adjacent the upmr surface or the elevator bar I58 and the spindle is is extended upwardly as is illustrated in Fig. 5 a suihcient distance to be engaged by the sight line indicator 8i when the indicator coincides with the line drawn between the spindle is and the origin.

The sight line indicator 6! may be insulated as by means of insulating material 91 and may thus form one contact of an electric switch, the other contact of which comprises the spindle 15:. This switch may be included in a suitable electric circuit adapted to eflect the release of the bomb so that as soon as the sight line indicator 89 is moved to a point corresponding to the proper bomb release point, the firing circuit will released.

The foregoing description has been based on the assumption that the plane was pursuing the proper course and no wind corrections were required. The panel indicator it is employed to permit the pilot to fly the plane in the proper course. This indicator mechanism is illustrated diagrammatically in Fig. 7 as comprising 2. normally fixed reference line indicator 92 and a course indicator 93. These indicators may comprise suitable thin pointer members mounted coaxially with respect to each other and adapted to be moved into coincidence with each other whenever the plane is being flown along the proper course. Accordingly the pointer 92 is secured to a shaft 94 which is journaled within a hollow shaft 95 to which the pointer 93 is secured, the hollow shaft 95 being iournalled in a suitable supporting bracket 96 which may be attached to the rear side of the instrument panel 20.

The shafts st and are both drivably connected by means of the transmission system Hi to the sighting device ll. One form of transmission system 18 which may be employed is illustrated in Fig. '7 as comprising a pair of flexible cables 5'1 and 55 comprising sheath menb bers 99 within which is mounted a freely rotatable torsion member I 00. The shaft 94 may frame 2I.

As is illustrated in Figs. 4 and 5,- the hollow shaft IIII is provided with a lever I08 pivotally secured as at I09 to a link 0. The link IIO may be pivoted as at III to a lever II2 which is in turn pivotally supported as at II3 upon the upper end of the stub shaft 38. The lever H2 is also pivotally secured as by means of a pivot Ill to a second link II5 which is passed through the hollow. shaft 81 and pivotally secured at its inner end as at IIS to the telescope supporting bracket 83. The link H5 preferably includes a universal or ball Joint II'I permitting the link Hi to be rotated as a result of pivotal movement of the telescope I5 about the axis of the shaft 81 without requiring a corresponding pivotal movement of the inner-end of the link at the pivot 'II i.

It will be noted that the trunnions 85 are dis posed below the center of the hollow shaft 81, whereas, the link pivot H6 is disposed substantially on the center of that shaft. Thus, pivotal movement of the telescope about the trunnions 85 will produce a corresponding. longitudinal movement of the link III: which, through the medium of the lever I I2, link IIfl and lever I08, will be translated into a corresponding angular movement of the hollow shaft l ll. This angular movement of the shaft I 01 will be transmitted through the transmission system I8 to produce a corresponding angular movement of the pointer 83 with respect to the normally stationary pointer 92.

If, therefore, the plane is flying along a course which will pass to one side of the objective, the observer in order to train the telescope I5 on the objective must move the telescope I5 from a vertical plane to an angular plane and will thereby cause a corresponding angular shifting of the pointer 93. The pilot by observing the position of the pointer 93 with respect to the pointer 92 will be apprised of the fact that the plane is not pursuing a course which will pass directly above the objective and will, therefore, gradually change the course of the plane in the proper direction to pass over the objective.

As the course of the plane is changed by the pilot, the position in which the telescope I5 must be placed in order to maintain its line of sight trained on the objective will also change, and this change will be indicated to the pilot by the movement of the pointer 93. Thus, the pilot need only correct his course right or left in such manner as to maintain the pointer 93 aligned with the pointer 92. When this alignment obtains the pilot is assured that the plane is following the correct course and so the lateral pothe pointer 23 and quadrant 24 to align the longitudinal axis of the sighting device with the actual course of the plane relative to the ground surface. The bombardier may, by suitable means such as a comparison of the drift angle wifhthe speed of the plane, determine the magnitude of the cross wind component This may be introduced into the device as a corrective factor by means of a crank I18 which is coupled by means of gearing II9, I20 and I2I to a pointer I22 adapted to indicate on a dial I23 the direction (1. (2., right or left) andmagnitude of the cross wind component. The gearing IIB, I20 and I2I serves also to drivably interconnect the pointer I22 with the shaft I06 so that the angular position of the shaft I06 may be changed in accordance with the magnitude of the cross wind component. This shifting of the shaft I06 through its coupling to the normally stationary indicator 92 will similarly shift the position of the determination of the bomb release point in accordance with the magnitude of a head or tail wind component. This component will hereinafter be referred to as a. head wind component, it being realized that the head and tail wind components are identical except that they are in opposite directions.

The bombardier after having determined the head wind component may set a pointer I25 to a point indicating on a dial I25 the magnitude of the head wind component. The pointer I24 may be drivably secured to a gear I26 which may be engaged with a rack I21. The rack I2I may in turn engage a gear I28 which is drivably connected to a crank I29 permitting the pointer I24 to be appropriately positioned by merely rotating the crank I29. The rack I21 is also secured as by means of a pin and slot connecting device I30 to an angularly shiftable arm I3I which is pivotally secured to the origin of the mechanism as by surrounding the stub shaft 36.

The angular shifting of the arm .I3I which results from setting the pointer I26 to indicate the magnitude of the head wind represents the actual magnitude of the head wind and not the amount of correction which must be made to the determined bomb release point. As previously pointed out, the amount of such correction may be considered to be a linear function of the altitude of the plane with respect to the objective.

Accordingly the member ISI 15 provided with an elongated slot I32 into which a pin I33 extends. The pin I33 is passed upwardly through a slot I34 formed in a guide member secured to the elevator bar 58 (see Figs. 4 and 6). The lower end of the pin I 33 is secured to an endless band i36 which is confined between side flanges I31 extended downwardly from the member I35 and passed over a pair of band supporting rollers I38 and I39. The roller I33 is an idler roller, being supported upon a stub shaft aau eec I40 extended between the side plates I31. The roller IE3) is slidably but non-rotatably carried on a transversely extending shaft I I, the skirts I31 being notched as indicated at I82 to receive the shaft Mi. 4 I

' The shirt: I31 engage the sides the roller I39 and serve to slide the roller along the shaft I as the elevator bar 58 and the supporting member I35 are moved along the axis of the locus curve 3| by operation of the feed screws 55 and 66. In so moving the engagement of the pin I33 with the slot I32 causes a movement of the pin in in the slot I34, the amount of such movement being proportional to the angular positioning 0! the member I3I with respect to the axis oi the locus curve 34 and being also proportional to the position of the elevator bar 58 with respect to the origin of such curve. This proportional movement 01 the pin I83 is translated by means of the band I36 and the roller I39 into a corresponding proportional rotation of the shaft I H.

The shaft MI is connected by bevel gears I42 to a cross shaft I43 which is in turn connected as by means of bevel gears I to a pointer I45 mounted concentrically with the pointer I24 and adapted to indicate on the scale I a proportional head wind magnitude. 1 The absolute value of this proportional head wind magnitude is of no importance but is merely indicative of the extent to which the head wind magnitude is corrected in terms of the altitude of the plane with respect to the target.

As was pointed out in connection with Fig. 3,

the head wind correction distance I separating the ideal bomb release point K with the release point L corrected for head wind represents merely the difference in location between the origin of the trajectories 5 and 8. As was pointed out in connection with Fig. 2 the origin of each of the trajectories, such as trajectories 2 and 5, for the same altitudes but different speeds likewise are separated by a horizontal distance which is proportional to the difference between the two speeds. Consequently the corrective distance 1 may be embodied in changing the shape of the locus curve 3% by an appropriate amount.

Accordingly I provide a crank N6 which is connected by means of gearing I41 to a third pointer hi8 mounted coaxially with the pointers I24 and I45. The bombardier after having e mployed the crank I29 to set the pointer I 24 to indicate the magnitude of the head wind component and thereby setting the pointer I45 to the corrected head wind component value now operates the crank I46 to move the pointer I48 to a position coincldentwith the pointer I45. The

' crank I44; is also connected by means of gearing I49 to the mixing gear 48-30 so that the movement of the pointer I 48 to coincidence with the pointer M5 is accompanied by a proportional angular movement of the step cone pulley 39, with the result that the shape of the locus curve 34 is thereby changed from the ideal to a corrected curve taking into account the effect of with respect to ground, the magnitude of the head and cross wind components and the angle of drift of the plane.

Each of these factors may be set up by the bombardier through the use of the previously described apparatus and when these factors are thus set up, there is generated a locus curve 34 upon which there is located the spindle I9 at a point corresponding to the proper bomb release point.

The observer. by merely keeping the telescope I5 trained on the target, eflects first the transla tion to the pilot of the plane the necessary information to permit the pilot to guide the plane along its proper course and, second, efiects the release of the bomb automatically at the time the plane arrives at such release point.

It will be observed that the bombardier may, by continually checking the aircraft instruments against the dials provided on the sighting de vice of my invention, continually correct the setting of the sighting device in accordance with such changes in the conditions as may occur from time to time. Thus it is insured that at the instant of bomb release, the release point has been accurately and correctly determined with respect to the conditions actually existing at the instant of bomb release. There is thus avoided the difficulties previously encountered in setting the sighting device and then attempting to fly the plane at the speed, altitude and course required to conform to the setting of the sighting device.

It will be similarly noted that the device of my invention avoids the timing errors inherent in the other sighting devices wherein it was necessary to manually trip the bomb releases at the instant the image of the objective passed the cross-hairs of the sighting devices. As compared with this manual operation, it is an exceedingly simple and easy operation for an observer to merely maintain the telescope I 5 trained on the objective, this being sufficient to automatically sheet the release of the bomb at the time the plane arrives at the bomb release point.

While I have shown and described the preferred embodiment of my invention, I do not desire to be limited to any of the details of construction shown or described herein, except as defined in the appended claims.

I claim:

1. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb, the

combination of: curve forming means on said aircraft for producing a curve representing on a reduced scale the locus of all points from wh ch a bomb releasedfrom said aircraft will fall upon an objective represented by the origin of said curve; sighting means for defining a sighting line tra nable on said objective; sight line indicating means mounted for pivotal movement about the origin of said curve; and means cupling sad indicating means for movement in correspondence with the angular movement of said sighting line relative to said objective, whereby arrival of said aircraft at the correct bomb release point is indicated by the arrival of the intersection of said indicating means with said curve at a point corresponding to the elevation of said aircraft with respect to said objective.

2. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb, the combination of: curve forming means on said aircraft for producing a curve representing on a reduced scale the locus of all points from which a bomb released from said aircraft will fall upon an objective represented by the origin of said curve; control means for identifying the point on said curve which corresponds to the elevation of said aircraft with respect to said objective;

sighting means for defining a sighting line trainline relative to said objective, whereby arrival of said aircraft at the correct bomb release point is indicated by the arrival of said indicating means at coincidence with a line joining said control .means and the origin of said curve.

3. In a bomb sight for useon an aircraft having means for carrying and releasing a bomb, the combination of curve forming means on said aircraft for producing a curve representing on a reduced scale the locus of all points from which a bomb released from said aircraft will fall upon an objective represented by the origin of said curve; means for adjusting the shape of said curve to conform to the'speedof said aircraft; sighting means for defining a sighting line trainable on said objective; sight line indicating means mounted for pivotal movement about the origin of said curves; and means coupling said indicating means for movement in correspondence with the angular movement of said sighting line relative to said objective, whereby arrival of said aircraft at the correct bomb release point is indicated by the arrival of the intersection of said indicating means with said curve at a point corresponding to the elevation of said aircraft with respect to said objective. 4. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb, the combination of: curve forming means on said aircraft for producing a curve representing on a reduced scale the locus of all points from which a .bomb released from said aircraft will fall upon an objective represented by the origin of said curve; control means for identifying the point on said curve which corresponds to the elevation of said aircraft with respect to said objective; means for moving said control means along said curve in accordance with changes in said elevation; sighting means for defining a sighting line trainable on said objective; sight line indicating means mounted for pivotal movement about the origin of said curve; and means coupling said indicating means for movement in correspondence with the angular movement of said sighting line relative to said objective, whereby arrival of said aircraft at the correct bomb release point is indicated by the arrival of said indicating means at coincidence with a line joining said control means and the origin of said curve.

5. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb, the combination of: curve forming means on said aircraft for producing a curve representing on a reduced scale the locus of all points from which a bomb released from said aircraft will fall upon an objective represented by the origin of said curve; means for adjusting the shape of said curve to conform to the speed of said aircraft; control means for identifying the point on said curve which corresponds to the elevation of said aircraft with respect to said objective; means for moving said control means along said curve in accordance with changes in said elevation; sighting means for defining a sighting line trainable on said objective; sight line indicating means mounted for pivotal movement about the origin of said curve; and means coupling said indicating means for movement in correspondence with the angular movement of said sighting line relaive to said objective, whereby arrival of said aircraft at the correct bomb release point is indicated by the arrival of said indicating means at coincidence with a line joining said control means and the origin of said curve.

6. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb, the combination of: curve forming means on said aircraft for producing a curve representing on a reduced scale the locus of all points from which a bomb released from said aircraft will fall upon an objective represented by the origin of said curve; means for adjusting the shape of said curve to conform to the speed of said aircraft; means for further adjusting the shape of said curve to compensate for the effect on the flight of said bomb of a wind component parallel to the course of said aircraft; sighting means for defining a sighting line trainable on said objective; sight line indicating means mounted for pivotal movement about the origin of said curve; and means coupling said indicating means for movement in correspondence with the angular movement of said sighting line relative to said objective, whereby arrival of said aircraft at the correct bomb release point is indicated by the arrival of the intersection of said indicating means with said curve at a point corresponding to the elevation of said aircraft with respect to said objective.

7. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb, means defining a curve representing on a reduced scale the locus of all points from which a bomb released from said aircraft when approaching an objective at a predetermined speed will fall upon said objective.

8. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb,

means defining a curve representing on a reduced scale the locus of all points from which a bomb released from said aircraft when approaching an objective at a predetermined speed will fell upon said objective, and means for changing the equation of said curve to correspond to speeds other than said predetermined speed.

9. In a bomb sight for use on an aircraft having means for carrying and releasing a bomb,

means defining a curve representing on a reduced scale the locus of all points from which a bomb released from said aircraft when approaching an objective at a predetermined speed will fall upon said objective, and means for changing the shape of said curve in accordance with variations in the speed of said aircraft from said predetermined speed.

10. A curve generating device for use in a bomb sight for an aircraft having means for carrying and releasing a bomb comprising: a flexible member; means for holding one end of said member fixed; and means for springing said member into a curved form representing on a reduced scale the locus of all points from which a bomb will fall upon an objective represented by the fixed end of said member upon release of said bomb from an aircraft approaching said objective at a predetermined speed. 7

11. A curve generating device for use in a bomb i ht, r an aircraft having means for carrying and releasing a bomb comprising: a flexible member; means for holding one end of said member fixed; a plurality of movablemembers engaging said flexible vmember at points spaced along its length: guide means for defining parallel paths oi movement for said movable members: and means for moving said members to predetermined positions relative to each other and relative to said fixed end to thereby spring said flexible member into a curved form.

12. A curve generating device for use in a bomb sight for an aircraft having means for car- 10 tying and releasing a bomb comprising: a flexible member; means for holding one end of said member fixed; a plurality of movable members engaging said flexible member at points spaced along its length; guide means for defining par- 15 rates to thereby spring said flexible member into a curved form.

13. A curve generating device for use in a bomb sight for an aircraft having means for carrying and releasing a bomb comprising: a

1 flexible member; means for holding one end of said member fixed; a plurality of movable members engaging said flexible member at points spaced along its length; guide means for defining parallel paths of movement for said movable members; and means for simultaneously moving said members away from a position aligned transversely of the lengths of said guide means at different rates to thereby spring said flexible memher into a curved form, said rates being so adjusted as to produce a curve of substantially parabolic form.

CLARENCE G. AXI'MANN. 

